AZ-305 infrastructure solutions explained
Design infrastructure solutions is the largest AZ-305 domain at 30–35%. It spans four areas: compute, application architecture, migrations and networking. Together they make up about a third of the exam, so this is where preparation pays most. Every question gives requirements and asks for a recommendation, and the winning answer is the one that meets them with the least operational overhead.
Design compute solutions
| Option | Choose it when |
|---|---|
| Virtual machines and scale sets | You need OS control, lift-and-shift, or software that cannot be containerised |
| App Service | You run a web app or API and want a managed platform with slots and autoscale |
| Azure Container Apps | You run containers or microservices, want scale to zero and event-driven scaling, and do not want to run Kubernetes |
| Azure Kubernetes Service | You need the full Kubernetes API, custom operators or fine control of the cluster |
| Azure Container Instances | You run short-lived or simple containers without orchestration |
| Azure Functions | Short, event-triggered code where you pay per execution |
| Azure Batch | Large numbers of independent or tightly coupled compute tasks |
When a scenario says “minimal management”, move up the table toward the managed options. When it says “needs a specific kernel module” or “licensed software tied to a VM”, move down. Specify the components too: VM size family for memory or compute-heavy loads, GPU sizes for rendering and training, and Spot VMs for interruptible work.
Design an application architecture
Messaging and events
The distinction between messages and events is tested constantly:
| Service | Model | Typical use |
|---|---|---|
| Service Bus | Messages for reliable enterprise messaging: queues, topics, sessions, dead-lettering, ordering | Order processing, workflows where each message must be processed |
| Event Grid | Reactive events: something happened, subscribe to it | Reacting to blob created, resource changes, webhooks |
| Event Hubs | High-throughput event streaming | Telemetry, logs, clickstreams |
| Storage queues | Simple, cheap queue | Basic decoupling with large backlogs |
A message is a command or work item the sender cares about; an event is a notification the sender does not track. If ordering, transactions or dead-letter handling are mentioned, think Service Bus.
API integration, caching and configuration
- API Management publishes, secures and throttles APIs: subscription keys, rate limits, policies, versioning and a developer portal.
- Azure Logic Apps integrates systems with workflows and connectors.
- Azure Cache for Redis reduces latency and database load for hot data and sessions.
- Azure App Configuration holds settings and feature flags centrally; pair with Key Vault for secrets.
- Automated deployment points to infrastructure as code (Bicep or Terraform) and pipelines, with deployment slots or blue-green for low-risk releases.
Design migrations
Migration questions follow the Cloud Adoption Framework: plan, ready, adopt, govern and manage. At recommend level:
- Assess servers, databases and applications with Azure Migrate, which discovers machines, shows dependencies and estimates sizing and cost.
- Choose a strategy per workload: rehost (lift and shift), replatform (for example SQL Server to Managed Instance), refactor (rebuild for PaaS or containers), or retire.
- Migrate databases with Azure Database Migration Service, using online mode when downtime must be minimal.
- Migrate files and unstructured data with Azure Data Box for large volumes or slow links, and AzCopy or Azure File Sync for network transfers.
Pick the migration tool by workload type, and prefer assessment before any move.
Design network solutions
Connectivity
| Need | Service |
|---|---|
| Encrypted tunnel over the internet to on-premises | VPN Gateway |
| Private, predictable bandwidth to on-premises | ExpressRoute |
| Many branches and regions with transitive routing | Virtual WAN |
| Connect two VNets | Peering (not transitive) |
| Private access to a PaaS service | Private endpoint |
| Outbound internet from private subnets | NAT Gateway |
Hub-and-spoke is the standard topology: shared services in a hub VNet, workloads in peered spokes, central inspection through Azure Firewall.
Load balancing and routing
Decide on two axes: global or regional, and HTTP (layer 7) or any protocol (layer 4).
| Regional | Global | |
|---|---|---|
| Layer 7 (HTTP/S) | Application Gateway | Front Door |
| Layer 4 | Load Balancer | Cross-region Load Balancer |
| DNS-based | Traffic Manager |
Application Gateway and Front Door both offer WAF; Traffic Manager only answers DNS.
Performance and security
Optimise performance with proximity placement, accelerated networking, CDN or Front Door caching, and ExpressRoute for latency-sensitive hybrid links. Optimise security with NSGs, Azure Firewall, private endpoints, DDoS Protection, WAF and Bastion for admin access.
Worked example
A company moves an on-premises order system and a public site to Azure with minimal operations staff. A sound design: Azure Migrate assessment, SQL Managed Instance through Database Migration Service in online mode, App Service for the site, Service Bus between order intake and fulfilment, Redis for catalogue caching, Front Door with WAF for global traffic, and a site-to-site VPN now with ExpressRoute planned.
Practice questions
Question 1. An order system must pass each order to a fulfilment service. Orders must be processed once, in order per customer, and failed messages must be set aside for inspection. Which service should you recommend?
- A. Azure Event Grid
- B. Azure Service Bus with sessions and dead-lettering
- C. Azure Event Hubs
- D. Azure Cache for Redis
Show answer
Answer: B
Service Bus offers sessions for ordering per key, peek-lock processing and dead-letter queues. Event Grid delivers lightweight event notifications without per-customer ordering or a work queue. Event Hubs is built for high-volume streaming, not message-by-message settlement. Azure Cache for Redis is a cache, not a messaging system.
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Question 2. A small team runs ten containerised microservices that scale on HTTP traffic and queue length, some down to zero. The team has no Kubernetes experience and wants minimal infrastructure management. What should you recommend?
- A. Azure Container Apps
- B. Azure Kubernetes Service with self-managed node pools
- C. Azure Container Instances for every service
- D. Virtual machines with Docker installed
Show answer
Answer: A
Azure Container Apps runs containers on a managed platform with event-driven scaling, including scale to zero, and without cluster administration. AKS gives full control but needs Kubernetes expertise. Container Instances has no built-in autoscaling or service-to-service features. Plain VMs add full OS management.
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Question 3. A company must move 300 on-premises servers to Azure. Before deciding what to move and how, it wants to discover the servers, map the dependencies between them and estimate Azure sizing and cost. Which service should you recommend first?
- A. Azure Site Recovery
- B. Azure Database Migration Service
- C. Azure Migrate
- D. Azure Data Box
Show answer
Answer: C
Azure Migrate discovers servers, visualises dependencies and produces sizing and cost assessments, which is the first step in the Cloud Adoption Framework approach. Site Recovery handles replication for DR or migration after planning. Database Migration Service moves databases only. Data Box transfers large data volumes physically.
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What to do next
Take the practice test for a mixed check, or read AZ-305 exam tips for how to read these questions. For the comparison with the DevOps exam, see AZ-305 vs AZ-400.